Rheostat



(No Model.) J. L, GISH RHBOSTAT.

No. 408,345. Patented May 14, 1889.

N, PiTEns. Plmmvuumgmpner. Wmingwnf, a

UNITED STATES PATENT OFFICE.

JOHN L. GISII, OF JACKSON, MICHIGAN.

RH EO STAT.

SPECIFICATION forming part of Letters Patent No. 403,345, dated May 14, 1889.

Application filed January 16, 1889. Serial No. 296,512. (No model.)

To @ZZ whom t may concern.-

Be it known that I, JOHN L. GISH, a citizen of the United States, and a resident of J ackson, in the county of Jackson and State of Michigan7 have invented new and useful Improvements in Rheostats, of which the following is a specification. v

This invention relates to a rheostat which is provided with a series of resistance-coils and a movable contact-point which bears against one of the coils and to which one end of the instrument-line is connected, so that the contact-point can be adjusted along the coil for the purpose of regulating the shunted current. A rheostat of this description is described and shown in an application for patent filed by me July l2, 1888, Serial No. 279,742. In this rheostat the movable contact-point reaches only a single coil, and when two or more coils are arranged to be partially shunted each coil is provided with a separate contact-point. In such a rheost-at the instrument-line has to be shifted from one movable contact-point to another when the adjustment is extended beyond one coil, whereby the shunted current is intercepted and other inconveniences and objectionable results are produced.

The object of my present invention is to construct the rheostat in such manner that a single movable contact-point canbe adjusted along two or more coils, thereby increasing the range of adjustment and avoiding any interruption of the shunted current while the adjustment of the contactpoint is being made.

In the accompanying drawings, Ifigure l is an elevation of a rheostat provided with my improvementsA Fig, 2 is a horizontal section thereof. Fig. 3 is avertical section of the movable contact-point on an enlarged scale. Figs. -i and 5 are cross-sections in. lines fr 1r and y 31j, Eig. 3, respectively.

Like letters of reference refer to like parts in the several. figures.

A represents the base, a the top piece, and b the upright board, constituting the frame of the rheostat.

C represents the generator; o, the line running from the generator to the binding-post (l of the rheostat at which the current enters the latter; d', the binding-post at which the current leaves the rheostat, and c the line extending from the binding-post d to the generator.

E E E ELE5 EGE? represent a series of connected resistance-coils secured to the frame of the rheostat and having the outer ends of the end coils, E El, connected, respectively, with the binding-posts d d.

As shown in the drawings, the eoils E, E', E2, and E3 are arranged to be partially shunted out by means of a movable contact-point, F, to which one end of the instrument-line f is connected, while the other end of said line is connected with the binding-post d. The lower ends of the coils E E are connected by a fiat metallic bar, g, the upper ends of the coils EL EL by a similar bar, g', and the lower ends of the coils E2 E8 by a similar bar, g2.

H II II2 H3 represent upright slots or Ways formed on the vertical board li of the frame opposite the coils E E E2 E3. rEhe lower ends of the slots I-I l'Il are connected by a horizontal slot, 71 opposite the metallic bar g, the upper ends of the slots II H2 by a horizontal slot, h', opposite the bar g', and the lower ends of the slots H2 HS by a slot, h2, opposite the bar g2, so that the upright and horizontal slots form a continuous slot or way opposite these coils and their connecting-bars. The movable contact-point F is arranged in this continuous slot or way, so that it can be adjusted in the same along these coils and their connecting-bars without breaking' contact in passing from one coil to the other. This contactpoint is constructed in the following manner:

I represents a sliding traine arranged in the slot or way of the rheostat-rame and provided on opposite sides of the board b with iianges zi '1?'. The portion of the sliding frame which enters the slot is made square, so as to pass snugly through the vertical and horizontal portions of the slot and support the contact-point in whatever position it is placed.

J represents the binding-post of the movable contact-point, to which the end of the instrument-line f is attached. This bindingpostis provided with a socket, j, which enters the outer sleeve portion, a?, of the sliding frame I. rlhc soclretj carries a projectiomj, which plays in a quadrant-shaped slot, f, in the sleeve ff, and limits the rotary movement of the socket i in the sleeve 'i2 to a quarterturn. This projection, engfi'ging in said slot,

IOO

' in the socket j, whereby the bolt is compelled to turn with the socket and at the same time permitted to move lengthwise in the socket in adjusting itself to the coil.

When the movable conta'ctpoint is placed at the upper end of the vertical slot H opposite the outgoing end of the coil E, the shunted current is of minimum strength. By moving the contact-point downwardly to the lower end of the coil E, then across to the lower end of the coil E and then upwardly along the latter coil, the strength of the shunted current is gradually increased, and in this manner the contact-point is moved along and from one coil to another until the desired current is shunted out. This arrangement does away .with the interruption of the shunted current in adjusting from one coil to another, and enables a high tension ofthe shunted current to be reached gradually, which is especially desirable when using a dental lamp, as the carbon loops of such lamps are liable to break when a current of high tension is suddenly applied. It also avoids a multiplicity of movable contact-points, and simplifies the construction of the rheostat. In passing from a coil to a connecting-bar, or vice versa, the socket is given a quarter-turn, thereby placing the anti-friction roller in the proper position to run freely. The anti-friction roller is held by the spring in close contact with the coil or connecting-bar, so as to insure the proper passage of the shunted current. While the anti-friction roller described and shown is preferably used, it is not indispensable, and may be omitted.

I claim as my invention- 1. The combination, with two resistancev5c connection, substantially as set forth.

3. The combination ,with several resistancecoils having their adjacent ends connected by iiat metallicv bars, of a frame provided opposite said coils and bars with a continuous slot or way, and a movable contact-point arranged in said slot or way, substantially as set forth.

4. The combination, with a resistance-coil, of a stationary frame provided with a slot or way opposite said coil, a sliding frame, I, arranged in said slot or way, a binding-post, J, provided with a socket, j, arranged in said sliding frame, and a contact-bolt, K, and spring lo, arrangedin said socket, substantially as set forth.

5. The combination, with a resistance-coil,

of a stationary frame provided with a slot orA way opposite said coil, a sliding frame, I, arranged in said slot and provided with asleeve, 2, having a slot, j?, a binding-post, J,vpro vided with a socket, j, arranged in the sleeve 2 and having a projection, j', entering the slot j?, a contact-bolt, K, provided with an anti-friction roller, K', and having a proj ection l enterinfy a 0froove Z in the socket and a spring, la, arranged in said socket behind the contact-bolt, substantially as set forth.

Witness my hand this 11th day of January, 1889.

JOHN L. GISH.

Witnesses:

SAM H. CAMP, JNO. G. MUNDY. 

